2001
DOI: 10.1107/s0108767301010698
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Abstract: The electron-density distribution of the high-pressure polymorph of SiO 2 , stishovite [a = 4.177 (1) , c = 2.6655 (5) A Ê , space group P4 2 amnm, Z = 2], has been redetermined by single-crystal diffractometry using synchrotron radiation of 100.42 and 30.99 keV, respectively, in order to obtain essentially absorptionand extinction-free data. Room-temperature diffraction experiments on two samples of irregular shape were carried out on two different diffractometers installed at HASYLAB/DESY, Hamburg, Germany. … Show more

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Cited by 71 publications
(54 citation statements)
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“…The optimized cell parameters and a list of calculated and observed d-spacings of the symmetry-allowed refl ections for both phases are given in Table 1. The cell volume of stishovite in our experiment (49.71 Å 3 ) is 7 to 8.8% larger than pristine stishovite at ambient conditions (Kirfel et al 2001). This fi nding is not a surprise, since the present stishovite sample is the result of a structural recovery process upon cold compression of amorphous material.…”
Section: Resultsmentioning
confidence: 87%
“…The optimized cell parameters and a list of calculated and observed d-spacings of the symmetry-allowed refl ections for both phases are given in Table 1. The cell volume of stishovite in our experiment (49.71 Å 3 ) is 7 to 8.8% larger than pristine stishovite at ambient conditions (Kirfel et al 2001). This fi nding is not a surprise, since the present stishovite sample is the result of a structural recovery process upon cold compression of amorphous material.…”
Section: Resultsmentioning
confidence: 87%
“…For the prediction of scattering intensities for individual phonon branches the CASTEP code output was employed as an input to scripts operating under Mathcad# computing the dynamical structure factor, S(Q, E), using standard formalism [Burkel, 2000]. Diffraction-derived thermal parameters were implemented [Kirfel et al, 2001]. The availability of the S(Q, E) permits to localize the Brillouin zones providing the highest intensity and the best contrast for a given phonon.…”
Section: Computational Detailsmentioning
confidence: 99%
“…At room temperature and static conditions, α‐quartz transforms to coesite with fourfold coordinated Si at 2 GPa, and to stishovite with sixfold coordinated Si (Stishov and Popova ) at 8 GPa (Kirfel et al. ). Notably, coesite‐bearing impactites indicate higher shock pressures than those containing stishovite, in contrast to quasi‐static environments.…”
Section: Introductionmentioning
confidence: 99%
“…The pressure and temperature required for the formation and preservation of high-pressure phases of quartz seem to be different when comparing impact environments with quasi-static conditions (Carl et al 2017). At room temperature and static conditions, a-quartz transforms to coesite with fourfold coordinated Si at 2 GPa, and to stishovite with sixfold coordinated Si (Stishov and Popova 1961) at 8 GPa (Kirfel et al 2001). Notably, coesite-bearing impactites indicate higher shock pressures than those containing stishovite, in contrast to quasi-static environments.…”
Section: Introductionmentioning
confidence: 99%